For the imprinting of a printing substrate e.g. of a single sheet or of a web-like printing substrate of the most variable materials, such as e.g. paper or thin plastic or metal films it is known to produce image-dependent charge images on a charge image carrier, e.g. a photo conductor, the charge images corresponding to the images to be printed, comprised of regions to be inked and regions not to be inked. The regions of the charge images to be inked are developed with a developer station by a color medium, e.g. toner or color particles. Then the developed images are reprinted on the printing substrate and fixed there.
A fluid developer containing at least toner and carrier fluid can in the process be used for inking the charge images. A method for such an electrophoretic fluid development (electrographic development) in digital printing systems is e.g. known from W/2007/57387 (US 2008/279597 A1). In the process a carrier fluid containing silicon oil with toner dispersed within is used as a fluid developer.
In the case of the printing device in accordance with WO2007/57387, a loading station, an element for image-wise exposure (character generator), a developer station for the development of the charge images with toner to toner images, a transfer station for reprinting of the toner images on a printing substrate and an element for cleaning of the photo conductor drum after reprinting are arranged along a charge image carrier. The toner images are fed to the printing substrate by the charge image carrier via the transfer station and are reprinted on the printing substrate. For this purpose a transfer roller or a transfer belt is used, the transfer roller or transfer belt taking the toner images e.g. embedded in carrier fluid in the case of the use of a fluid developer and feeding them to the printing substrate. In the reprinting station the toner images are reprinted on the printing substrate and are then fixed there under pressure and using an electric field.
The fixing of the toner images on the printing substrate takes place in a fixing station which is arranged after the transfer station on the printing substrate. In the process the fixing can take place by heat and pressure. Heat is supplied to the printing substrate, through which the toner of the toner images is melted on, in order to coalesce closely to the printing substrate. Heated fixing rollers or radiant heaters can be employed for the supply of heat, the fixing roller or radiant heaters melting the toner images with heat and pressure or radiant heat.
From U.S. Pat. No. 4,538,899 (ED 3406290) in addition it is known to employ a carrier fluid in the case of the use of fluid developers for the fixing of the toner images, the carrier fluid being able to be oxidized. The toner images are transferred with the carrier fluid to the printing substrate. There the carrier fluid is evaporated, wherein the toner images are fixed on the printing substrate by the evaporated carrier fluid.